Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$17.53	6.388%	$18.6498	$18.65	$18.65	$18.60
Purchase #2	$247.89	10.779%	$274.6101	$274.61	$274.60	$274.60
Purchase #3	$83.55	13.179%	$94.5611	$94.56	$94.55	$94.60
Purchase #4	$237.72	9.396%	$260.0562	$260.06	$260.05	$260.10
Purchase #5	$38.77	9.241%	$42.3527	$42.35	$42.35	$42.40
Purchase #6	$235.33	9.178%	$256.9286	$256.93	$256.95	$256.90
Purchase #7	$111.32	3.385%	$115.0882	$115.09	$115.10	$115.10
7 purchase totals =	$972.11		$1,062.2467	$1,062.25	$1,062.25	$1,062.30